1. Field of the Invention
The present invention relates generally to a coffee making apparatus, and more particularly to a spray head for a coffee making apparatus having a plurality of raised holes on the interior surface of the spray head to resist clogging by deposition of lime and other sediments.
2. Description of the Related Art
Lixiviation is a general term for the passage of hot water through a ground product, where the hot water acts as a solvent. Coffee making machines use this technique to brew coffee. In a drip filtration system for brewing coffee, coffee grounds are placed in a basket and heated water is drained into the basket to mix with the grounds and extract flavoring solubles as the water is directed into a decanter positioned below the basket. A filter is placed between the grounds and the decanter to remove sediment and prevent the grounds from entering the beverage in the decanter.
Brewing the most flavorful coffee requires a balancing between the strength of the brewed coffee and the degree of extraction from the ground coffee. The coffee brewing process is made up of three stages: wetting, extraction, and hydrolysis. During wetting, as the coffee bean fiber absorbs hot water gas is driven from interstitial voids inside the coffee particles preparing the coffee particles for extraction of solubles. In the extraction stage, water-soluble flavoring compounds within the coffee bean fibers dissolve and enter the water. In the hydrolysis stage, large molecules of water-insoluble carbohydrates break down into smaller molecules that are water soluble.
To achieve uniform wetting and extraction, the hot water contacting the bed of ground coffee must preferably lift and separate the coffee grounds with a turbulent flow. Improperly applying the water to the grounds can contribute to a poorly brewed coffee. Conventional spray heads tend to concentrate the water flow in the center of the brew basket and do not disperse the grounds with an active attempt to create turbulence.
Another common problem in coffee making equipment such as a drip filtration system is liming, or scaling, caused by excessive hardness or mineral content of the water. Heating water containing these minerals causes the minerals such as lime to precipitate and form scale and sediment on the piping. The precipitate is especially problematic when it accumulates around the pores of the spray head to reduce the flow of the water. When the reduction in the level of flow reaches a critical level, the equipment must be serviced at significant cost, and the equipment cannot be used during this maintenance operation. Accordingly, for commercial purveyors of coffee who use such a system it would be preferable to prolong the periods between such maintenance if possible.
Another problem encountered by the drip filtration systems of the prior art is the inability of the spray heads to wet the grounds evenly and completely. Typically, the pores of the spray head are centrally disposed and the flow of water through the holes is concentrated about a central stream. When the stream comes in contact with the grounds, the grounds adjacent to the central stream tend to become saturated with the water while grounds further away from the central stream may not receive adequate exposure to the water. Even if the basket begins to fill with water, the peripheral grounds may be lifting by floating grounds below and only be partially wetted. This leads grounds that are over-saturated in some places and under-saturated in others, yielding a coffee brew that is inconsistent and not optimally flavored with the right blend of solubles. Moreover, the central stream of water will typically push aside grounds immediately below the central stream and generate a pool in the displaced grounds. The pool of water that forms immerses the grounds adjacent to the pool but the static nature of the pool is not beneficial to the extraction of the flavored solubles. Rather, it is desirable to promote turbidity within the grounds environment to move the individual grounds and thereby more fully extract the solubles. Moreover, the typical spray head is made of either a high temperature plastic or stainless steel, which has a porosity that tends to promote the accumulation of scaling and liming.
A discussion of the type of coffee makers that utilize spray heads can be found in U.S. Pat. No. 5,910,205 to Patel, the disclosure of which is incorporated fuilly by reference herein,and U.S. Pat. No. 5,477,775 to Delbom et al., the disclosure of which is incorporated fully by reference herein. Mork, U.S. Pat. No. 6,279,459 incorporated herein by reference, discloses a coffee maker with a rotating grounds basket in an attempt to disperse the water more evenly about the grounds basket. However, the complications associated with a spinning grounds basket make its implementation and use problematic. Dahmen, U.S. Pat. No. 6,244,162 incorporated herein by reference, discloses a coffee making apparatus with a spray head having an inner ring of pores and a ring of pores along an outer edge adapted to spray the grounds in a fan shaped pattern. These disclosures do not adequately address the problem oft he accumulation of lime and scaling at the pores of the spray head. The present invention seeks to overcome the shortcomings of the prior art systems discussed above.
The present invention is directed to a spray head for a coffee making apparatus that distributes a water flow pattern evenly over a surface area of grounds located below the spray head, and includes a configuration for reducing the accumulation of lime and sedimentation at the spray head exit holes by elevating the inlet of the holes above a lowermost surface. The raised holes allow the formation of lime and scaling to occur below and away from the inlets such that the inlets are not clogged as quickly and maintenance of the spray head can be deferred for longer periods of time. The raised holes are spaced from the lowermost floor by stand pipes having a vertical channel therethrough for communicating water at an accumulation level equal to the height of the stand pipe. The stand pipes can be cylindrical in shape at a base and include a tapered or beveled upper portion leading to the entrance of the vertical channel. The exit of the channel may include a frusto contical annul projection depending downward from the outside surface of the sprinkler member to resist water from adhering to the outside surface. The two-piece spray head of the present invention is preferably made of a polyetherimide material with a low surface porosity to further resist the accumulation of lime and other sedimentary deposits.
These and other features and advantages of the present invention will become apparent from the following detailed description of a preferred embodiment which, taken in conjunction with the accompanying drawings, illustrates by way of example the principles of the invention.